Continuous subcutaneous delivery of medication or monitoring of a body analyte is often accomplished using a cannula inserted into a human body that remains in place for several days. Diabetes patients may use such cannula, which is positioned in a subcutaneous compartment for continuous delivery of insulin by pumps or for monitoring interstitial glucose levels by sensors. A combination of a tube connecting the insulin pump to the cannula and a detachable connector is often referred to as an infusion set. Such infusion sets and modes of their insertion are disclosed, for example, in U.S. Pat. Nos. 4,755,173, 5,176,662 and 5,257,980. Subcutaneous cannula insertion modes for continuous glucose monitoring are discussed, for example, in U.S. Pat. Nos. 5,390,671, 5,568,806 and 5,586,553. Usually, trans-cutaneous (“hypodermic”) cannula insertion can be carried out with a sharp metal penetrating member to be withdrawn after skin piercing. This procedure can be carried out manually by the user/patient. The insertion is usually painful and requires considerable skill. Some patients are reluctant or hesitant to pierce their own skin, and thus, encounter difficulties in proper cannula insertion. Such difficulties can be attributed to insufficient manual dexterity or, alternatively, to anxiety associated with anticipated discomfort as the needle pierces the skin. This problem can be especially significant when an insulin pump is used, since misplacement of the cannula can cause kinking, incorrect insertion angle or incorrect cannula insertion depth leading eventually to cannula obstruction. As a result, delivery of insulin could be hampered thereby causing a life-threatening situation.
In an attempt to cope with this problem, automatic infusion set insertion devices (“inserters”) were developed to assure correct placement of a cannula into the subcutaneous layer at a correct angle while minimizing pain and hazardous obstructions associated with cannula insertion. U.S. Pat. Nos. 6,093,172 and 6,830,562 disclose inserters having a spring-loaded plunger for an automatic subcutaneous placement of an infusion set. These automatic inserters can be used with “pager like” pumps having long tubing and a cannula altogether constituting an “infusion set”. However, these devices cannot be used for insertion of a cannula used with skin adherable pumps that do not employ long tubing. Such device is discussed in U.S. Pat. No. 6,699,218 to Flaherty et al. In Flaherty's skin adherable device, the cannula is rigidly connected to the pump's housing. After adhesion to user's skin, the cannula is fired, thereby emerging from the device's housing and piercing the skin. Consecutively, the penetrating member is retracted back into the pump's housing. This device is relatively bulky, heavy and indiscreet because the spring-loaded mechanism is deployed within the device's housing during the entire period of usage. In addition, the cannula has only a single length size and penetrates the skin only at a certain angle; the patient cannot adjust these parameters based on various insertion sites and other clinical requirements.
Continuous glucose monitors are disclosed in U.S. Pat. Nos. 5,390,671 and 6,143,164, assigned to MiniMed and E. Heller & Company, respectively. These devices monitor glucose levels in the subcutaneous compartment using a sensor, which is inserted manually or automatically in a fashion similar to the insertion of a cannula, as disclosed in U.S. Pat. No. 7,110,803, assigned to DexCom.
Thus, it would be desirable to provide improved systems and methods for inserting a cannula and/or sensor into the body of a patient.